Congratulations to Mike. He joins 31 other current and retired members of the department who are FRS.

Mike says, with the help of ChatGPT (humorous version): "Delighted to be elected a Fellow of the Royal Society. I plan to celebrate in the traditional scientific way: mild astonishment, followed by tea."

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This week a neuroscientist and a mathematician talk about the challenges of collaboration. Here are Leo and Ramón.

Convergence and near-optimal sampling for multivariate function approximations in irregular domains via Vandermonde with Arnoldi
Zhu, W Nakatsukasa, Y IMA Journal of Numerical Analysis
Convergence and Near-optimal Sampling for Multivariate Function Approximations in Irregular Domains via Vandermonde with Arnoldi
NAKATSUKASA, Y IMA Journal of Numerical Analysis
Mind the gap: a spectral analysis of rank collapse and signal propagation in attention layers
Nait Saada, T Naderi, A Tanner, J
Mind the Gap: a Spectral Analysis of Rank Collapse and Signal Propagation in Attention Layers
Tanner, J
Tue, 20 May 2025
14:00
L6

Dehn functions of Bestvina--Brady groups

Matteo Migliorini
(Karlsruhe Institute of Technology)
Abstract

Bestvina--Brady groups were first introduced by Bestvina and Brady for their interesting finiteness properties. In this talk, we discuss their Dehn functions, that are a notion of isoperimetric inequality for finitely presented groups and can be thought of as a "quantitative version" of finite presentability. A result of Dison shows that the Dehn function of a Bestvina--Brady group is always bounded above by a quartic polynomial.

Our main result is to compute the Dehn function for all finitely presented Bestvina--Brady groups. In particular, we show that the Dehn function of a Bestvina--Brady group grows as a polynomial of integer degree, and we present the combinatorial criteria on the graph that determine whether the Dehn functions of the associated Bestvina--Brady group is linear, quadratic, cubic, or quartic.

This is joint work with Chang and García-Mejía.

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